Investigation of Governing Physics in a PEM Electrolyzer

Sammanfattning: Hydrogen gas is an energy source that has an energy density (per mass) that is three times as large than the energy density of natural gas. This qualifies hydrogen gas as a prime candidate for the fuel of tomorrow. One of the main research areas for hydrogen include the production of it as there are a vast amount of methods of hydrogen production. Renewable hydrogen can potentially be produced through water electrolysis, which is investigated in this thesis. The aim was to model and simulate the behaviour of a two-dimensional PEMEC using COMSOL Multiphysics 5.5. Once the model was complete and compared with experimental data from the literature, the model was used to investigate the losses that take place in a PEMEC by considering five various cases with different assumptions made in each case. To take it one step further, a sensitivity analysis was performed to determine to what extent the parameters would affect the system efficiency. In summary, the results showed that temperature contributed largely to the mass transport loss in the polarization curves. In general, the losses were larger for a higher temperature. Taking only the electrochemistry into account, resulted in the lowest loss at low current densities. Using a multi-phase model together with a water transport model yielded the largest loss at intermediate to high current densities, regardless of temperature. The sensitivity analysis showed that by doubling the catalyst layer thickness, a clear mass transport loss is visible, thus, showing that the catalyst layer thickness has a large effect on the model.